Implanted well breakdown in high voltage devices

摘要

An n-type isolation structure is disclosed which includes an n-type BISO layer in combination with a shallow n-well, in an IC. The n-type BISO layer is formed by implanting n-type dopants into a p-type IC substrate in addition to a conventional n-type buried layer (NBL), prior to growth of a p-type epitaxial layer. The n-type dopants in the BISO implanted layer diffuse upward from the p-type substrate to between one-third and two-thirds of the thickness of the p-type epitaxial layer. The shallow n-type well extends from a top surface of the p-type epitaxial layer to the n-type BISO layer, forming a continuous n-type isolation structure from the top surface of the p-type epitaxial layer to the p-type substrate. The width of the n-type BISO layer may be less than the thickness of the epitaxial layer, and may be used alone or with the NBL to isolate components in the IC.